A close friend of mine was fairly impressed by my transmitter detailed in my other topic "AM Transmitter Design" and said I should sell it. While I am not willing to put a transmitter with my current specs into production, something like it in the future I feel is something you guys would be interested in. The transmitter would at least have...

* A range of 100 feet* A comparator-LC design* A board-on-top-of-base design with (maybe?) an acrylic case (See past topic to get an idea)* A USB-B port for power* A built-on antenna (in fashion of mast antenna) with support for a BNC antenna* An ESD-tested design* The ability to transmit audio with non-crap quality* The ability to change frequency on the fly

I will only sell the transmitter if A: demand is sufficient B: the specs above are met. Your response will help me determine the features to add and the pricepoint to target.

This would more-than-likely be distributed in kit form in an attempt to bypass FCC registration (I don't have the money lying around to register it, of course)

And unlike what most people would think, the transmitter is turning out to be comparably stable to a crystal oscillator. I'm still testing it, but if the frequency hasn't changed at all in two hours I'm willing to call it stable

Also, leave any suggestions. I really appreciate feedback

P.S. If I do end up putting the thing into production, I'll buy an ad on the forum so you guys'll know

Last edited by Gip-Gip on Jan Wed 24, 2018 10:12 pm, edited 1 time in total.

Are you aware that you can't legally sell an assembled functional transmitter without FCC approval? Others have been charged with violation of the rules and fined, quite recently.

Presuming that you intend to sell it only as a kit, then there should be some market for it. Since the SSTran units are no longer being sold, you would want to meet or exceed the performance of those units as they were quite popular.

_________________Dennis

Experience is what you gain when the results aren't what you were expecting.

Are you aware that you can't legally sell an assembled functional transmitter without FCC approval? Others have been charged with violation of the rules and fined, quite recently.

Presuming that you intend to sell it only as a kit, then there should be some market for it. Since the SSTran units are no longer being sold, you would want to meet or exceed the performance of those units as they were quite popular.

I didn't know a Part 15 transmitter would fall under regulation. Turning the design into a kit however wouldn't be difficult...

Are you aware that you can't legally sell an assembled functional transmitter without FCC approval? Others have been charged with violation of the rules and fined, quite recently.

Presuming that you intend to sell it only as a kit, then there should be some market for it. Since the SSTran units are no longer being sold, you would want to meet or exceed the performance of those units as they were quite popular.

I didn't know a Part 15 transmitter would fall under regulation. Turning the design into a kit however wouldn't be difficult...

Yes, transmitters are under Part 15 and they have been regulated for a long, long time. It costs a fortune to get one type certified, people have said that you would never be able to sell enough units to pay for certification. The last guy the Feds caught selling them got fined a serious amount as well.

_________________Dennis

Experience is what you gain when the results aren't what you were expecting.

I appreciate the work you've put into this, but I have to echo Macrohenry's concern about frequency stability. On the schematic in your other thread, there's no crystal frequency reference. The oscillator appears to be a comparator with an RC/LC feedback loop. It would take some strong convincing to get me to accept that this would be stable.

I appreciate the work you've put into this, but I have to echo Macrohenry's concern about frequency stability. On the schematic in your other thread, there's no crystal frequency reference. The oscillator appears to be a comparator with an RC/LC feedback loop. It would take some strong convincing to get me to accept that this would be stable.[/url]?

I'll run a 24-hour test on the thing and measure the drift in frequency. I doubt there will be much drift, if any at all, as with previous experiments changing the timing of the comparator doesn't effect the frequency in a noticeable way.

BobWeaver wrote:

I think the most obvious question is: How does it perform compared to the highly regarded and simple LM386N MK-XI BCB Transmitter?

At it's core my design is not that complicated, and doesn't require a tuning slug/capacitor. I could honestly make something of my design cheaper if the parts were chosen correctly, and it would still have many features the BCB lacks.

Macrohenry wrote:

Is the 100 ft range indoors and full quieting?What frequency range?

Yes and ideally the full AM spectrum

While the 24 hour test is running I'll work on converting it into a kit.

I am not sure that the frequency stability would be an issue for vintage radios (within reason) If it is not used with a modern radio with PLL that is spot on some drift is OK as you can retune the receiver. My two tube transmitter is not crystal controled and works fine. After it and the radio get up to working temperature I tune it in and seldom need to adjust.

I would think a kit would have some market because not everyone wants to DIY and order parts from several vendors to get small quantities of cheap components with shipping costs. What would help is to get a few out and get some feed back on range, sound, stability, etc and see if any changes need to be made. The only issue I see is that the vintage radio market is somewhat limited. Talking House sells to multiple market segments.

You will get a thousand naysayers with all the reasons you will fail. If the risk is not too big, like losing your house, I would say go for it. I seem to recall a couple of guys both named Steve that cobbled together some computer kits in their garage on a shoe string for a market that didn't really exist.

1. Assess your competition and their products2. Figure out your break even point to produce them and estimate your potential margin3. Get some prototypes out and get feedback4. Tweek and adjust your plan5. Look for other potential market segments6. Have some fun with it

I am not sure that the frequency stability would be an issue for vintage radios (within reason) If it is not used with a modern radio with PLL that is spot on some drift is OK as you can retune the receiver. My two tube transmitter is not crystal controled and works fine. After it and the radio get up to working temperature I tune it in and seldom need to adjust.

My only objection to non-crystal controlled transmitters is the production of beat tones in the radio from adjacent and co-channel signals giving "wheee-o-wheee" sounds as the oscillator drifts in frequency. This is especially annoying at night when distant signals get stronger at the antenna. With accurate crystal control those beat tones are either 0Hz or 10kHz +/- the frequency error which is no more than a few tens of Hz.

Getting FCC certification runs about $10-20K, so that alone potentially adds hundreds to the cost of a transmitter on top of parts, materials, profit margin, etc. assuming one sells at least 100 units, so not cost effective for a transmitter designed to be affordable. Kits fall into a gray area of FCC regulation, and one I can never seem to get a good answer on. They are either considered a finished product requiring certification or a DIY product which does not depending on who is making the determination. The FCC contradicts itself on this issue if you look into the enforcement actions regarding kits that were sold assembled.

I like the USB-B connector. You'd be able to use any printer cable. I was thinking of our portable (rechargeable) phone chargers. I could use one to power the transmitter and wouldn't need an AC outlet. Not sure how useful this is but think of how pure the DC would be! Plus, you can walk the transmitter around to find the best place to put it.

While I'd prefer a crystal controlled transmitter I agree thata simple L/C design would work fine for an AM BCB lowpower transmitter. After all the receivers use L/C local oscillatorssnd their drift is acceptable.

In your poll, my vote was 'no' but onlybecause I like designing and building my own stuff. Is therea need for a kit like this? Perhaps but may be more trouble thanits worth.Steve

_________________'cell phones and the internet are tools, not a lifestyle'

Is there a need for a kit like this? Perhaps but may be more trouble than Its worth.Steve

Even if no-one bought the kit I'd still enjoy making it in the first place

It's looking like I'll be making a kit available for ~$25 including base and etc. I've found a few suitable THT components that I can use and I'm greatly simplifying the design, hopefully reducing the cost..

I'll get a version 2 schematic done by the end of tomorrow and post it on the other thread.

Another business option would be to sell it on a royalty bases to computer manufactures. Their customers could stream their favorite music or radio station live to every old radio in the house. The manufacturer could spring for the $20k with the FCC and have more muscle with the FCC if it was met with resistance by the FCC. Overall marketing would be improved due to a new gadget for the public to play with. Trickle down might be more old radios get sold on ebay.

Another option that might generate more interest would be to make a board that will fit the Raspberry pi as there is an audio processing program called Stereo Tools that has a version for the pi. Perhaps even include the pi with the necessary programs, case, keyboard, display ETC... and the un-assembled transmitter board so that all one has to do is solder the parts on the board, plug it into the pi and turn it on.

One could then have a completely self contained transmitter with built in processing and music source.

North Georgia, near Pendergrass to be exact. Nice to see another Georgian!

Tube Radio wrote:

Another option that might generate more interest would be to make a board that will fit the Raspberry pi as there is an audio processing program called Stereo Tools that has a version for the pi. Perhaps even include the pi with the necessary programs, case, keyboard, display ETC... and the un-assembled transmitter board so that all one has to do is solder the parts on the board, plug it into the pi and turn it on.

One could then have a completely self contained transmitter with built in processing and music source.

Might be a future project, but I see more of a need for at-least an "entry" level kit; I'm not so skilled with the Pi and a Pi-integrated unit would probably be fairly expensive. However, I do like the idea of a TV-Broadcasting Part-15 Pi..

bill hamre wrote:

Another business option would be to sell it on a royalty bases to computer manufactures. Their customers could stream their favorite music or radio station live to every old radio in the house. The manufacturer could spring for the $20k with the FCC and have more muscle with the FCC if it was met with resistance by the FCC. Overall marketing would be improved due to a new gadget for the public to play with. Trickle down might be more old radios get sold on ebay.

I'd honestly be surprised if a company would invest >$20k into what essentially boils down to a gimmick. I like the idea myself but I doubt the mass of consumers are going to be streaming to their radios when they have superior tech that'll do the same. Maybe make like a little USB transmitter, but any further than that would probably not be worth the time.

Finalizing a V2 BOM. Things are looking a little more pricey than expected, so I might actually target the $40 range. However, the V2 BOM also includes many debugging features and a variable inductor for smoothly changing frequency, so the price may go down (or at least be more justified).